A national competitor since the 1900s and the Canadian champion in 1913, William Barnes was selected to represent Canada in trap shooting at the 1924 Summer Olympics, where he won a silver medal in the team event alongside George Beattie, John Black, James Montgomery, Samuel Newton, and Samuel Vance. This team also came in third at that year’s British Championships. By career he was a contractor, having inherited a quarrying business from his father, Thomas William, Sr., in 1901, and added contracting and excavating to its operations, in addition to expanding its holdings and properties. He died in 1925, just under a year and half after earning his Olympic medal, and the business passed to his son Rolph, who had competed in the 1,500 metres at the same Olympics as his father. The company was eventually acquired by Opta Minerals Inc.